aboutsummaryrefslogtreecommitdiffstats
path: root/arch/xtensa/lib/memset.S
blob: 4de25134bc62aa2f4ce939175e0e0eee4f278201 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
/*
 *  arch/xtensa/lib/memset.S
 *
 *  ANSI C standard library function memset
 *  (Well, almost.  .fixup code might return zero.)
 *
 *  This file is subject to the terms and conditions of the GNU General
 *  Public License.  See the file "COPYING" in the main directory of
 *  this archive for more details.
 *
 *  Copyright (C) 2002 Tensilica Inc.
 */

#include <xtensa/coreasm.h>

/*
 * void *memset(void *dst, int c, size_t length)
 *
 * The algorithm is as follows:
 *   Create a word with c in all byte positions
 *   If the destination is aligned,
 *     do 16B chucks with a loop, and then finish up with
 *     8B, 4B, 2B, and 1B stores conditional on the length.
 *   If destination is unaligned, align it by conditionally
 *     setting 1B and 2B and then go to aligned case.
 *   This code tries to use fall-through branches for the common
 *     case of an aligned destination (except for the branches to
 *     the alignment labels).
 */

/* Load or store instructions that may cause exceptions use the EX macro. */

#define EX(insn,reg1,reg2,offset,handler)	\
9:	insn	reg1, reg2, offset;		\
	.section __ex_table, "a";		\
	.word	9b, handler;			\
	.previous


.text
.align	4
.global	memset
.type	memset,@function
memset:
	entry	sp, 16		# minimal stack frame
	# a2/ dst, a3/ c, a4/ length
	extui	a3, a3, 0, 8	# mask to just 8 bits
	slli	a7, a3, 8	# duplicate character in all bytes of word
	or	a3, a3, a7	# ...
	slli	a7, a3, 16	# ...
	or	a3, a3, a7	# ...
	mov	a5, a2		# copy dst so that a2 is return value
	movi	a6, 3		# for alignment tests
	bany	a2, a6, .Ldstunaligned # if dst is unaligned
.L0:	# return here from .Ldstunaligned when dst is aligned
	srli	a7, a4, 4	# number of loop iterations with 16B
				# per iteration
	bnez	a4, .Laligned
	retw

/*
 * Destination is word-aligned.
 */
	# set 16 bytes per iteration for word-aligned dst
	.align	4		# 1 mod 4 alignment for LOOPNEZ
	.byte	0		# (0 mod 4 alignment for LBEG)
.Laligned:
#if XCHAL_HAVE_LOOPS
	loopnez	a7, .Loop1done
#else /* !XCHAL_HAVE_LOOPS */
	beqz	a7, .Loop1done
	slli	a6, a7, 4
	add	a6, a6, a5	# a6 = end of last 16B chunk
#endif /* !XCHAL_HAVE_LOOPS */
.Loop1:
	EX(s32i, a3, a5,  0, memset_fixup)
	EX(s32i, a3, a5,  4, memset_fixup)
	EX(s32i, a3, a5,  8, memset_fixup)
	EX(s32i, a3, a5, 12, memset_fixup)
	addi	a5, a5, 16
#if !XCHAL_HAVE_LOOPS
	blt	a5, a6, .Loop1
#endif /* !XCHAL_HAVE_LOOPS */
.Loop1done:
	bbci.l	a4, 3, .L2
	# set 8 bytes
	EX(s32i, a3, a5,  0, memset_fixup)
	EX(s32i, a3, a5,  4, memset_fixup)
	addi	a5, a5,  8
.L2:
	bbci.l	a4, 2, .L3
	# set 4 bytes
	EX(s32i, a3, a5,  0, memset_fixup)
	addi	a5, a5,  4
.L3:
	bbci.l	a4, 1, .L4
	# set 2 bytes
	EX(s16i, a3, a5,  0, memset_fixup)
	addi	a5, a5,  2
.L4:
	bbci.l	a4, 0, .L5
	# set 1 byte
	EX(s8i, a3, a5,  0, memset_fixup)
.L5:
.Lret1:
	retw

/*
 * Destination is unaligned
 */

.Ldstunaligned:
	bltui	a4, 8, .Lbyteset	# do short copies byte by byte
	bbci.l	a5, 0, .L20		# branch if dst alignment half-aligned
	# dst is only byte aligned
	# set 1 byte
	EX(s8i, a3, a5,  0, memset_fixup)
	addi	a5, a5,  1
	addi	a4, a4, -1
	# now retest if dst aligned
	bbci.l	a5, 1, .L0	# if now aligned, return to main algorithm
.L20:
	# dst half-aligned
	# set 2 bytes
	EX(s16i, a3, a5,  0, memset_fixup)
	addi	a5, a5,  2
	addi	a4, a4, -2
	j	.L0		# dst is now aligned, return to main algorithm

/*
 * Byte by byte set
 */
	.align	4
	.byte	0		# 1 mod 4 alignment for LOOPNEZ
				# (0 mod 4 alignment for LBEG)
.Lbyteset:
#if XCHAL_HAVE_LOOPS
	loopnez	a4, .Lbytesetdone
#else /* !XCHAL_HAVE_LOOPS */
	beqz	a4, .Lbytesetdone
	add	a6, a5, a4	# a6 = ending address
#endif /* !XCHAL_HAVE_LOOPS */
.Lbyteloop:
	EX(s8i, a3, a5, 0, memset_fixup)
	addi	a5, a5, 1
#if !XCHAL_HAVE_LOOPS
	blt	a5, a6, .Lbyteloop
#endif /* !XCHAL_HAVE_LOOPS */
.Lbytesetdone:
	retw


	.section .fixup, "ax"
	.align	4

/* We return zero if a failure occurred. */

memset_fixup:
	movi	a2, 0
	retw